1. Field of the Invention
The present invention relates generally to a semiconductor structure and process thereof, and more specifically, to a semiconductor structure and process thereof, which laterally etches a part of a recess to make parts of the recess have different widths or different slopes of sidewalls.
2. Description of the Prior Art
With increasing miniaturization of semiconductor devices, various Fin-shaped field effect transistor (FinFET) devices have been developed. The Fin-shaped field effect transistor (FinFET) is advantageous for the following reasons. First, manufacturing processes of Fin-shaped field effect transistor (FinFET) devices can be integrated into traditional logic device processes, and thus are more compatible. In addition, since the three-dimensional structure of the FinFET increases the overlapping area between the gate and the substrate, the channel region is controlled more effectively. This therefore reduces drain-induced barrier lowering (DIBL) effect and short channel effect. Moreover, the channel region is longer for the same gate length. Therefore, the current between the source and the drain is increased.
The Fin-shaped field effect transistor (FinFET) includes a plurality of fin-shaped structures, and gate structures disposed across them. Therefore, the sidewall of the upper part of the recess between each fin-shaped structure is covered by gate structures and the inclined angle of the sidewall of the upper part of the recess would affect the shape of gate structures. In general, the sidewall of the upper part of the recess is preferred to be a vertical sidewall for approaching the demands of the gate structures disposed across the fin-shaped structures, thereby the electrical performance of the Fin-shaped field effect transistor (FinFET) can be achieved. However, the sidewall of the recess etched by current processes has an inclined angle that can not approach the structural demand of a Fin-shaped field effect transistor (FinFET).